Currently, the third generation mobile system phones, wireless LAN systems and the like are each managed and operated by different providers. Thus, using plural services operated by plural providers requires signing up with each provider to subscribe the each service. In such a case, each provider owns a unique system, and thus, a terminal identifier which is necessary for network connection (for example, an IP address) is independently assigned to each system. Accordingly, plural IP addresses are generally required to use plural systems at the same time.
The bandwidth no more than 6 GHz, such as VHF, UHF and low microwave band, is suitable for mobile communication systems. However, the bandwidth has been used densely for the third generation mobile phones and wireless LAN, and tight condition of frequency has been a serious problem. Given the problem, frequency bandwidths necessary for mobile communications for which the needs are high must be secured while utilizing the tight condition of frequency effectively and efficiently. For that, a technique for achieving high utilization of common use of radio waves among systems which use different radio waves such as mobile communications must be attained.
The IT Strategic Headquarters in the Ministry of Internal Affairs and Communications has been trying to achieve such a technique in “e-Japan Priority Policy Program-2004” The program has been established in June 2004 for the purpose of achieving, by 2011, practical use of radio communication systems for establishing an optimum communication environment by accurately determining requirements for applications to be used and radio wave conditions of the neighbors, and flexibly making selections including frequency bandwidths, modulation mode and duplex mode.
In order to achieve such radio communication systems, the idea of “cognitive radio” for recognizing radio conditions and controlling resources of radio systems according to the radio conditions was published in 1999. For example, the cognitive radio technique is disclosed in Mitora, “Cognitive radio for flexible mobile multimedia communications”, 1999 IEEE Int Workshop on Mobile Multimedia Communications Digest (November 1999), and Mitora, et.al., “Cognitive Radio: Making Software Radios More Personal”, 1999 IEEE Personal Communication, Vol. 6, No. 4 (1999).
However, there are various approaches for achieving the cognitive radio and the approaches have been studied.
FIG. 1 shows an entire configuration of a system connected to plural radio systems according to a conventional technique. An example in FIG. 1 shows that the following three systems are connected: cdma 1xEVDO (1xEvolution Data Only) as a cellular system, WiMAX as a radio broadband system for outdoor use in urban areas and wireless LAN (wireless Local Area Network) as a broadband system for indoor use and short distances. Hereinafter, these three systems are used as examples for explaining a radio system of this invention, however, this invention is applicable to other radio systems having the functions equivalent to these three.
A system comprises a terminal 101 for communicating with the plural radio systems, access points 102, 103 and 104 for each radio system, gateways 105, 106 and 107 for terminating the each radio system, Authentication Authorization and Accounting (AAA) 109, 110 and 111 provided for the each system for user authentication, and an HA (Home Agent) for receiving by proxy a packet to be transmitted to a network to which a terminal apparatus normally belongs, and for forwarding the packet to the terminal apparatus. For example, the EVDO system includes the access point 102, packet data serving node (PDSN) 105 as a gateway, and EVDO-AAA (Authentication Authorization Accounting) 109 as an AAA. The wireless LAN system includes the access point 103, packet data interworking function (PDIF) 106 as a gateway, and WiFi-AAA 110 as an AAA for wireless LAN. The WiMAX system includes the access point 104, access service network gateway (ASN-GW) 107 as a gateway, and WiMAX-AAA 111 as an AAA.
The gateways 105, 106 and 107 for terminating the each system, the HA 108, and AAA 109, 110 and 111 are connected to each other via a network 112.
The access points 102, 103 and 104 for the each radio system are radio base stations for terminating radio links of the terminals.
The gateways such as PDSN 105, PDIF 106 and ASN-GW 107 each acts as an FA (Foreign Agent) for the HA 108, and terminate the radio systems. The FA accommodates the terminal apparatus in the network to which the terminal apparatus belongs. Moreover, the FA receives a packet to be transmitted to the terminal apparatus from the HA 108 in downlink and transmits the packet transmitted from the terminal apparatus to the HA 108 in uplink. In FIG. 1, although one access point is connected to one gateway of a radio system, the number of access points is not limited to one. Generally, plural access points are connected to each gateway.
In the conventional radio system, each of the systems is independently operated, and thus, AAA 109, 110 and 111 are independently provided as shown in FIG. 1. Therefore, user authentication is independently performed for every use of the each radio system.
At this time, the HA 108 monitors which radio system the terminal apparatus is currently using for communication. More specifically, PDSN 105 in EVDO, PDIF 106 in wireless LAN and ASN-GW 107 in WiMAX function as the FA when looked from the HA. The HA 108 holds an association between an IP address of the gateway in the radio system which is currently communicating and an IP address assigned to the terminal.
Next, explained with reference to FIG. 2 is a method for acquiring the IP address assigned to the terminal, a process in a case of switching a system to be used based on reasons such as moving of the terminal, and an association between the gateway and the IP address of the terminal.
When the terminal 101 is connected to EVDO, terminal authentication using PAP/CHAP is performed between the terminal 101 and PDSN 105 as shown in a connection procedure 201. Upon completion of the terminal authentication performed by PDSN 105, an access request from the terminal 101 is transmitted to EVDO-AAA 109. As a response to the request, EVDO-AAA 109 transmits information such as an IP address (IP=a.b.c.d) to be assigned to the terminal, DNS information and an IP address (IP=1.2.3.4) of the HA to PDSN 105. The IP address is then assigned to the terminal after PDSN 105 forwards the information from EVDO-AAA 109 to the terminal 101. At this time, the HA 108 holds an association 202 between the IP address (IP=a.b.c.d) of the terminal and an IP address (IP=x.x.x.x) of PDSN acting as the FA.
In a case where, for example, the terminal is to newly connected to a different wireless LAN system from EVDO by moving (205) as shown in a connection procedure 203, for example, terminal authentication is performed using IKEv2 between the terminal and PDIF 106 which is a wireless LAN gateway. Upon completion of the terminal authentication performed by PDIF 106, an access request from the terminal 101 is transmitted to the WiFi-AAA 110.
As a response to the request, WiFi-AAA 110 transmits information such as an IP address (IP=e.f.g.h) to be assigned to the terminal, DNS information and the IP address (IP=1.2.3.4) of the HA to PDIF 106. The IP address is assigned to the terminal after PDIF 106 forwards the information to the terminal 101 from WiFi-AAA 110. At this time, the HA 108 holds an association 204 between the IP address (IP=e.f.g.h) of the terminal and an IP address (IP=y.y.y.y) of PDIF acting as the FA.
As has been described, in the conventional system, the switching among the plural radio systems requires user authentication for each system and different IP addresses are assigned to the terminal along with the switching among the systems. In addition, the user authentications are performed from the terminal through the gateway every time the radio system is switched, and thus, the switching takes second order time. In a case of a handover in which plural gateways are connected in the same system, no switching of systems occur even the terminal moves. Accordingly, the same IP address is assigned to the terminal. This is shown in FIG. 3.
When the terminal 101 is connected to the wireless LAN, as described with reference to FIG. 2 and as shown in the connection procedure 203, after the user authentication using IKEv2 is performed, the IP address (IP=e.f.g.h) of the terminal is assigned by the WiFi-AAA 110. In a case where the terminal moves (303) and is under different PDIF in the same wireless LAN system, another terminal authentication between the terminal 101 and PDIF 304 to be connected is performed as shown in a connection procedure 301. The WiFi-AAA 109 checks that the terminal has been already registered in the same system in order to assign the same IP address.
At this time, the HA 108 recognizes that the terminal 101 is in handover status. In other words, the terminal 101 is in a state of being able to forward data via the both gateways. Accordingly, both of PDIF 106 and PDIF 304 are registered as the FAs in an association 302. At this time, the data from its corresponding node on the network side checks the association 302 held in the HA 108 and is multicasted to each of PDIF 106 and PDIF 304.
When the handover of the terminal 101 is then completed and the terminal 101 is completely connected only to PDIF 304 which is the destination, only the IP address of the FA which is IP=z.z.z.z is associated with the IP address of the terminal which is IP=e.f.g.h in the association 302.
As has been described, in the conventional system, the HA 108 is capable of holding plural FA addresses for one IP address of the terminal in the same system. However, in this case, data to be transmitted to the terminal 101 is multicasted to each FA. In addition, user authentication is performed each time the gateway changes, and thus takes second order time for switching the radio system.